Musculoskeletal - Equine Flashcards
1
Q
What are the radiographic signs of non-union?
A
- > 3 months
- Radiolucent line through the fracture site
- Sealing off of the medullary cavity
- Bone resorption or regional osteoporosis above and below the fracture site
2
Q
Radiographic signs of physitis:
A
- Abnormal widening and widening and bony irregularlity at the epiphyseal and metaphyseal margins of the gowrth plate
- The metaphysis of the bone is boradened and assymetrical
- There is increased opacity of the metaphysis adjacent to the physis, which may be more irregular in appearance than normal, with paralle radiolucent lines reflecting retained cartlage cones
- The crotices of the metaphysis may be thick
- Soft tisseu swelling over the area of involvement is common
- Widened metahyseal and physeal bone may perisst throughout life, resulting in an irregular or flared appearance at the location of the physcal scare, although in many cases, considerable modelling towards normality occurs
- Most common site:
- Distal radius
3
Q
Equine primary bone tumors
A
- Primary tumors and metastatic malignancy of the long bones of horse are rare
- The majority of tumors involve bone occur in the skull or ocassionally the spine
4
Q
Osteitis and osteomyelitis
A
-
Osteitis = inflammation of bone. ‘
- Usually a result of trauma or inflammation in adjacent tissues.
- It is characterized by new bone formagtion and sometimes bone resorption.
- Differentiation should be made between aseptic osteitis and infectious osteitis.
- More common in adult horse
-
Osteomyelitis = inflammation of cortical bone and its myeloid cavity
- More common in foals
- May occur simultaneously at several sites, often extending to adjacent joints
5
Q
Hallmarks of equine osteitis
A
- Soft-tissue swelling with bone destruction and new bone formation
- An attempt to wall off infection resulting in radiopaque bone formaing adjacent to the area of bone infection and destruction
- Infection of bone may result in formation of a swquestrum surrounded by an involucrum (adjacent granulation tissue). A radiolucent tract may be visible extending from the infected area (a sinus).
- NOTE: the distal phalanx, distal sesamoid (navicular) bone and skull show a slightly different reaction to infection. In these bones, infection tends to cause destruction of bone with little evidence of new bone formation.
6
Q
Equine osteomyelitis
A
- Mroe common in foals than adults
- Can occur in many different sites and may extent to adjacent joints
- Osteomyelitis in foals tends to be very destructive and there is usually very little response by the bone to wall off the infection
7
Q
Hypertrophic Osteopathy in Horses
A
- Formerly known as Marie’s disease
- It has been shown that pulmonary involvement is NOT a pre-requisite as previoulsy beliced
- Mainly affects the metaphyses and diaphyses of the long bones, while sparing joints
- Typified by periosteal new bone that often appears to be forming perpendicular to the cortices of the bone and is irregular in outline in the acute stage
- In early stages, soft exposures must be used to avoid overexposure this relatively lucent new bone
- Later the margins of the new bone become more opaque and smoother, and the appearance of the original cortex of the bones becomes less clear
- The bony lesions develop secondary to a primary lesion usually in the thorax or ocassionally in the abdomen, such as tumors, an abscess or granulomatos disease
- Bone lesions may regress and remodel if the undelrying cause is treated
8
Q
Enostosis-like lesions
A
Enostosis: ~ panosteotis in dogs
- Bone developing within the medullary cavity or on the endosteum, resulting in a region of increased radiopacity
- Focal or multifocal, intramedullary sclerosis
- They usually happen in the dipahyseal region of long bones, near the nutrient foramen, often develooiung on the endosteal surface of bones
- The etiology and clinical significant is unknown. However, they may be associated with lameness and resolve with rest.
Scintigraphy:
- Frequently associated with focal increased radiopharmaceutical uptake, wheter or not they are causing lameness.
Differentials:
- Such focal radiopacitis should be differentialted from endosteal callys secondary to a fatigue or stress fracture
9
Q
Fracture description:
A
- Location
- Which bone
- What part of the bone
- Type of fracture
- Transverse
- Oblique
- Spiral
- Unicortical or bicortical
- Simple vs. open
- Multiple or comminuted
- Ahether articular involvement is present
- DEgree of displacement
- Concurrent pathology which adverse influcen the prognosis
10
Q
Salter Harris Type Fractures
A
“Prison Makes Every Boy Cry”
11
Q
Infectious arthritis
A
Radiographic features include:
- Periarticular soft tissue swelling
- Joint capsule distention, with or without apparent widening of the joint space
- Irregularity of outline of the subchondral bone
- Lucent zones in the subchondral bone, with or without areas of increased opacity
- Periarticular osteophyte formation, sude to secondary degenerative joint disease
- Partial collapse of subchondral bone
12
Q
What is Synovial Osteochondromatosis?
A
Overview:
- It is a very unusual synovial response in the horse and ca be primary vs. secondary.
- The condition described metaplastic and focal formation of cartilage within the intimal layer of the synovial membrane. Cartilage may undergoe mineralization and become evident radiographically.
Treatment:
- Arthroscopic removal of osteochondral bodies and rescetion of abnormal synovium.
Prognosis:
- Recurrence is quite common and malignant transformation rarely occurs, although, to this date has not been reported in horses.
13
Q
Pedal Osteitis Complex
A
Simply means inflammation of the distal phalanx. Septci vs. aspectic etiologies.
Radiographic findings:
Modelling of the solear margin of the bone:
- Changes are most evident on the dorsoproximal-palmarodistal oblique projections.
- The solar margins of the bone loses it smooth, opaque outline due to deminieralization.
- In some cases the bone near the solaer margin may have some increased radiolucency, making its visualization difficult.
- In more severe cases, larger areas of bone may be resorbed from the solear margin of the bone, resulting in apperant widening of the vascular channels primaryly at the solear margin.
- On the lateromedial projection, these changes may be evident as modelling ofthe tip of the bone, the solear margin no longer having a straight outline but curving proximally towards the dorsal aspect of the bone. This change appears magnified if the radiograph is not a true lateromedial projection.
- In more advances cases, more bone may be laid down on the dorsal surface of the bone at the toes.
Changes to palmar process of the distal phalanx:
- Best assessed in the dorsoproximal-palmarodistal oblique projections
- Discrete circular radiolcuent areas, 2mm-3mm in diamete, are present in the palmar processes of the bone, and these may be associated with new bone, particularly on the axial surfaces of the palamr process.
- There may be change in shape with elongation of the palmar processes, seen also in a dorsolateral-palmaromedial oblique view.
Mineralized lesions on the dorsal aspect of the distal phalanx may be seen:
- These are usually midway between the proximal border and loear margins of the bone
- The etiology is unknonw, although may be a reflection of abnormal stress on the suspensory apparatus of the distal phalanx
Causes:
- Concussion of the bone
- May be related with poor foot conformation and shoeing imbalances
Physical exam:
- May be associated with lameness that is most significant on hard surfaces
Treatment:
- Corrective trimming and shoeing
Diagnosis:
- Although condition may resolve clinically, the radiological changes usually remain throughout life
- Nuclear scintigraphy may help determine the significance of these radiographic changes within the distal phalanx. Increased radiopharmaceutical uptake would indicate active bone remodeling.
14
Q
Keratoma
A
General:
- The most common space-occupying mass to involve the distal phalanx is a keratoma.
- May occur at any point of the hoof wall
- May cause lameness as it enlarges and may be associated with secondary infection
- Treatment is by surgical removal of the keratoma and carries a reasonable prognosis although the mass may recurr up to several years later, especially if removal is incomplete.
Radiographic findings:
- Mass occupying mass
- Pressure from the mass on the dorsal aspect of the distal phalanx causes resorption bone. This is most easily seen at the solear margin of the bone, where a distinct semicircular notch is evident on a dorsoproximal-palmarodistal oblique view. This has a smooth outline, the bone undelying the keratoma frequently having increased opacity, which helps to differentiate this lesion from infection.
- There is usually no new bone associated with the lesion.
15
Q
Ossification of Ungual Cartilages
“Sidebone”
A
General:
- Some ossification of the ungular cartilages is a common finding, particularly in heavy breeds, cob-types and large British native ponies. Ossification usually occurs from the base of the cartilage at its attachemnt to the distal phalax and extends variablye distance proximally.
- Mild ossification is usually of no clinical significance. It is usually bilaterally symmetrical.
- If there is assyemteryc within a foot, the lateral cartilage is usually more extensively ossified.
- Marked assyemetry is usually unusual and may be associated with lameness.
- There may be one or more separate centers of ossification, which will be difficult to differentiate from fractures. Scintigraphy and MRI (increased signal intensity on fat-suppresion images).
- MRI is needed to diagnose soft tissue injury
16
Q
Enthesyophyte adjacent to the Extensor Process of the Distal Phalanx
A
The common digital extensor inserts immediately distal to the extensor process of the distal phalanx. Tearing of the insertion may result in lameness and entheseophyte formation of the proximodorsal aspect of the distal phalanx immediately dstal to the extensor process.
This change must be differentiate from the normal variation in shape of the extensor process.
The outline caused by the entheseophyte is usually irregular, and there may be alterations in the opacity of the trabecular structure of the underlying bone.
17
Q
A
18
Q
Osseous changes to the insertion of the deep digital flexor tendon and distal sesamoidean impar ligament
A
The deep digital flexor tendon and distal sesamoidean impar ligament insert on the fascia flexoria of the distal phalanx, in a smoothly outlined concavity. The compact bone at this site should be smooth and regular.
Insertional injury of the deep digital flexor tendon, or less commonly, the distal sesamoidean impar ligament may result in irregular new bone formation or an ill-defined lucent area of the normally uniform opque bone. This is usually associated with lameness.
Additional diagnostics: may provide additional information
- Transcuneal ultrasound
- MRI
- Contrast enhanced CT
19
Q
Subluxation of the distal interphalangeal joint
A
Dorsopalmar subluxation:
- Usually result of partial or cpmplete disruption of the deep digital flexor tendon.
- It is best identified on a lateromedial projection.
- There is mild widening of the joint space and the middle phalanx is displaced in a palmar direction.
Mediolateral subluxation:
- Occurs as a result of disruption of the collateral ligament of the distal interphalangeal joint.
- This can be difficult to identify in radiographs obtained with the foot bearing weight evenly. “Stressed” dorsopalmar radiographs may reveal abnormal widening of the joint sapce.
- The prognosis is very guarded.
20
Q
Fractures of the distal phalanx
(common sites)
A
A facture classification has been proposed although not all fractures fit this moder:
- Type 1: non-articualr fractures of the palmar or plantar process
- Type 2: articular fractures that are not mid-sagittal and extend from the distal interphalangeal joint to the medial or lateral aspect of the solear margin
- Type 3: articular mid-sagitall fracures of the distal phalanx
- Type 4: extensor process fracture
- Type 5: multifragments fractures
- Type 6: non-articular fractures involving the solear margin, and extending from one point of the solear margin to another
- Type 7: non-articular fractures of the palmar or plantar process of the distal phalanx in foals
21
Q
Chronic laminitis
A
Radiographic findings:
- The primary radiographic findings associated with laminitis include chnages to dorsal hoof wall and lamellar structures.
- Inflammation, streching, or separation of the lamellae, and separation of distal phalanx from the hoof wall resulting in rotation and/or shrinking of the distal phalanx.
- The hoof-distal phalanx distance may be increased
- *<20 mm**
- Increase in the ratio of hoof-distal phalanx distance: palmar length >27%
- In a normal foot there is a raduiolucent “halo” between the distal phalanx and both the hoof wall and sole. This is the lamellae and sublamellar dermis. Narrowing of this halo or increase in its opacity may reflect abnrmal lamellar epidermis, with the fromation of a lamellar wedge of amorphous horn.
- Rotation of the distal phalanx reflex loss of dunction of the suspensory apparatus of the distal phalanx due to lamellar stretching and separation, with the toe moving distally and away from the hoof wall. This results in the dorsal wll of the hoof ceasing to be parallel to the dorsal wall of the distal phalanx.
- As the condition progresses, on very high-quality radiographs, a faint radiolucent lines may appear between the distal phalanx and sole or hoof wall. This initially represent serum collected between the dermal and epidermal laminae and is visible becuase of the slight difference between fluid and horn densities. Subsequently this radiolucent line may become more apparent indicting necrotic laminar tissue.
- The degree of rotation may be important in assesing prognosis. Generally the more marked the rotation and faster it progresses, the worse the prognosis.
- Infection of the laminar tissue may be a complication of laminitis. This may result in gas shadows, ecident as areas of increased radiolucency between the distal phalanx and hoof wall, or distal phalanx and sole.
- “Sinker syndrome” is a very severe form of laminitis where the entire distal phalanx sinks within the hoof capsule. Measure the distance between the coronary band and the extensor process of the distal phalanx and can be compared between radiographs.
Treatment:
- Systemic treatment
- Corrective ferriery
22
Q
Venography and Laminitis
A
In a normal horse the laetral and medial digital veins, capillaries and arteries are filled in a retrograde manner, permitting visualization of the termina arch, coronary plexus, sublamellar vessles, circumflex veins, and veins in the solear and terminal papillae. The contrast material stays within the vessels and the distal phalanx is proximal to the circumflex vein.
In laminitis there may be alteration of the vasculature, notably compression of vessels in the coronary plexus, sublamellar plexus, terminal and solear papillae and the circumflex vein. There may be distribution of contrast material into abnormal soft tissues. Venography allows evaluation of the severity of vascular changes and can predict osseous pathology before it happerns.
23
Q
Long-toe low-heel complex
A
On a lateromdial projection of a normal foot, the center of the radius of curvature of the distal interphalangeal joint should be vertically above the center of the bearing surface of the foot. If the joint is over the palmar third of the bearing surface, this indicated poor dorsopalmar hoof balance which contirbute to lamenes.
On the lateromedial projection, it is also important to evaluate the solar margin of the distal phalanx relative to the ground. If the palmar process of the distal phalanx are closer to the ground than the toe, this indicated extreme poor hoof balance and is usually associated with lameness.
Palmarproximal-palmarodistal oblique views of the distal phalanx should be obtained in these cases, to look for abnormal radiolucent areas within the palmar process, irregularities of the margins of the plamar processes and for increased lucency around the palmar processes indicative of separation of the lamellae at the heel.
NOTE: These horses are painful on the palmar/plantar surface as apposed to the dorsal surface (as seen with navicular disease syndrome).
24
Q
Navicular Bone Syndrome
A
These horses are usually painful on the dorsal surface and tend not be responsive to shoeing or rest.
Radiographic findings:
Lateromedial projection:
- Enthesiophyte formation, and proximal or distal elongation of the plamar compact bone may develop
- The palmar compact bone may become thicker distally than proximally. In some cases the distal fossa may become more prominent.
Dorsoproximal/palmardistal oblique projection:
- There can be changes associated with teh lucent zines of the distal broder of the navicular bone, representing synovial invagination. The greater the number of lucent areas the greater the clinical significance.
- If there is a lucent area at the medial or lateral angle of the distal border of the navicular bone, it is liekly there is an associated distal border fragment. Fragments may occur laterally or medially.
- In advanced stages of the disease there may be an appreciable increase in opacity of the bone, with or without thickening of the plamar compact bone and loss fo definition between the palmar compact bone and the spongiosa. This warrants a very poor prognosis for treatmeht,
25
Endosteal reaction and enthesyophyte formation in the area of attachement of the **suspensory ligament**
The **suspensory ligament originates** from the proximal palmar aspect of the **metacarpal** bone. Tearing of attachment may result in enthesophytes formation (periostitis), due to subperiosteal hematoma formation, or endosteal new bone formation.
Radiographic examination may reveal a **localized increased opacity** in the **proximal** aspect of the bone with or without small patchy lucent zones.
26
Syndesmopathy between the 2nd & 3rd & 4th metacarpal bone
"Splints"
A **syndesmosis** is a slightly **movable articulation** where the contiguous bone surfaces are united by an interosseous ligament, e.g. the articulations between the 2nd, 3rd, and 4th metacarpal bone.
**Synostosis** means **fusion** of two bones. Focal or diffuse ossification of the interosseous ligament results in synostosis.
**Syndemopathy** refers to **injury of the syndesmosis** between the 2nd, 3rd, and 4th metacarpal (metatarsal) bones and alteration in adjacent cortical or trabecular architecture, with or without osseous spurs developing on the dorsal or palmar articular margins.
When **palpable** new bone develops between the 2nd, 3rd, and 4th metacarpal bones secondary to damage to the interosseous ligament, it is known as "**splint**".
27
Degenerative joint disease of the carpometacarpal joint
Radiographic signs:
* Narrowing of the carpometacarpal joint space
* Ill-defined lucent area of the distal aspect of the second carpal bone
* Generalized increased opacity of the trabecullary bone (modelling)
* Irregular periosteal new bone with overlying soft tissue swelling
* Periarticular osteophytosis
28
Physitis of the 3rd metacarpal bones
Radiographic signs:
* May result in enlargement of the bone and angular limb deformity of the metacarpophalangeal joint
* The metaphysis of the bone is broadened and asymmetrical
* There is increased opacity of the metaphysis adjacent to the physis, which may be more irregular in appearance than normal, with narrow vertical radiolucent lines or conical areas representing retained cartilage cores
* The cortices of the bone may be abnormally thickened
* The epiphysis may appear wedge shaped
Treatment:
* Correction of the deviation using radical trimming and or shoeing of the foot may be successful
* Surgical correction of the deviation may be necessary, it should be performed before 8 weeks of age, despite the "open radiographic" appearance of the physis
29
Common Fracture sites of the metacarpal/metatarsal bones
30
What are the 5 standard views of the equine carpus?
1. Lateromedial
2. Dorsopalamar
3. Dorsal 45° lateral-palmomedial oblique
4. Dorsal 45° medial-palmarolateral oblique views
5. Lateromedial flexed - helpful in separating the dorsodistal margin of the radial and inetrmediate carpal bones, where bone fragmentation and laetration in subchondral bone opacity frequently occur in racehorses.
31
What projection of the carpus could be helpful if degenerative joint disease is suspected?
Dorsal 75° lateral-palmoromedial oblique
&
Dorsal 75° medial-palmolateral oblique
\*\*required for Thoroughbred pre-sales\*\*
32
Normal lateromedial image of the carpus of a
5 day old foal
The distal aspect of the radius has 2 ossification centers. The lateral styloid process (morphologically the distal end of teh ulna) is spearat at birth and fuses in the first year.
Each carpal bone ossifies from a single center and is fully developed by 18 months of age.
33
Normal dorsopalmar projection of a
5-day old foal
34
Normal lateromedial projection of an adult carpus
The distal aspect of the radius has a prominent transverse ridge caudally, to which, medially and laterally, the medial and lateral collateral ligaments of the carpus attach. Immediately distal to the ridge are depressions for attachment of the carpal ligaments.
In a lateromedial projection the two rows of carpal bones are clearly delineated by the antebrachiocarpal, middle carpal and carpometacarpal joints.
On a **true lateromedial image**, the bone projected **most dorsally** in the proximal row of carpal bones is the **intermediate carpal**. Very **slight dorsolateral-palmoromedial obliquity** will make the **radial carpal** bone most prominent.
One or two **focal radiolucencies** may be seen in the soft tissues on the dorsal aspect of the antebrachiocarpal joint. These represent **fat in the joint** capsule and lie palmar to the synovial sheath of the extensor carpo radialis tendon. Distention of the joint capsule may obscure these lucent areas.
35
Dorsopalmar projection of adult carpus
A radiolucent canal is normally seen **between the radial** and **intermediate carpal** bones on this projection.
36
Osteochondromas
* Frequently identified on the caudodistal aspect of the radius in the metaphyseal region in the middle one-third of the bone
* They are variable in size and shape, and may have an irregular outline
* It is possible to identify a communication with the marrow cavity or the radius
* Although they may be benign and not associated with clinical signs, they may result in lameness, often with distention of the carpal sheath and lacerations of the deep digital flexor tendon
* The lesions are usually solitary but may be associated with lesions elsewhere
37
Fractures of the accessory carpal bone
* The most common fracture of the accessory carpal bone occur in vertical or slightly oblique plane just palmar to the groove for the tendon of ulnaris lateralis, an may be a result of a fall or occur during exercise
* There is often distention of the carpal sheath
* Displacement between pieces is most obvious during flexion
* The flexor tendon that insert on the palmar aspect of the bone may result in the palmar fragment being pulled proximally and medially
* Fragments may become displaced distally to the distal aspect of the carpal sheath, therefore radiographic examination of the metacarpus may also be indicated
* Bone fragments may impinge on the deep digital flexor tendon therefor ultrasonography is also recommended
Treatment:
* Tenoscopic removal of fragments may be indicated
* Prolonged rest (6-8 months)
* Healing is usually fibrous union and a lucent line persists
* Some horses develop chronic lameness, and tenoscopic assessment of the carpal sheath and transection of the palmar retinaculum may be indicated
* Internal fixation has been attempted with variably results
38
Physis of the shoulder joint
The **scapula** has 4 centers of ossification:
* The scapular cartilage
* The body of the scapula
* The cranial part of the glenoid cavity of the scapula - fuses by 5 months
* The supraglenoid tubercle - closes 12-24 months
The latter two can be partially ossified at birth and have a fuzzy, irregular outline.
The **proximal** **humerus** ossifies from three centers:
* The diaphysis
* The huemral head - the lesser tubercle develops from the same ossification center as the humeral head. It is usually incompletely ossified and fussy at birth.
* The greater tubercle
39
Mediolateral
Adult Shoulder
40
Mediolateral
Adult Shoulder
41
Cranial 45º medial-caudolateral oblique
Shuoulder
42
Mineralization of
Biceps Brachii Tendon
* Can occur as a sequel to a fracture of the supraglenoid tubercle but has also been described as a bilateral condition in association with degenerative joint disease
* It can also occur as a sequel to chronic tendonitis of biceps brachii
* Mineralization is most easily identified on the mediolateral projection
* The prognosis to future soundness is guarded
43
Abnormalities of the Scapulohumeral
Joint in Shetland Ponies
and
Miniature Horses
Dysplasia of the scapulohumeral joint, with or without subluxation of the scapulohumeral joint or secondary degenerative joint disease, has been seen in both Shetland Ponies and Miniature Horses
_Radiographic abnormalities include_:
* Flattening of the contour of glenoid articular margins of the glenoid cavity of the scapula and enthesophyte formation at the insertion of the joint capsule
* Mild subluxation of the joint is commonly seen
44
45
Physis of Elbow
The distal humerus develops from 3 ossification centers:
* Diaphysis
* Distal epiphysis
* Epiphysis of the medial epicondyle
The radius has a single proximal epiphysis and the ulna has a single proximal apophysis; the ulna may also have a separate center of ossification for the anconeal process.
At birth the ossification centers are rounded and may be irregular in outline because they are incompletely ossified.
46
Mediolateral Adult
Elbow
47
Periosteal proliferative reactions (enthesopathy) at the insertion of **biceps brachii** on the
radial tuberosity
48
Avulsion of the
**Deep Digital Flexor muscle**
from the medial epicondyle of the humerus
Unusual injury which may result in mild displacement of the bone fragment, with or without subsequent development of dystrophic mineralization within muscle
49
50
Common locations of fractures
of elbow region
51
Tarsus
| (foal)
52
Tarsus
| (foal)
53
Lateromedial Tarsus
54
Variation of medial trochlea tali
55
Dorsolateral-plantomedial oblique
Tarsus
56
Plantolateral - dorsomedial oblique
Tarsus
57
Dorsoplantar tarsus
58
Osteochondrosis
Radiographic findings include:
* A lucent are on the axial aspect of the medial malleolus or separation of a bony fragment at either the medial or (less commonly) the lateral malleolus of the tibia, or craniodistal aspect of the intermediate ridge of the tibia
* Bony fragments at the distal end of the medial trochlear ridge of the talus or lateral trochlear ridge of the talus
* Separation of a bony fragment from medial proximal tubercle of the talus
* An irregular, flattened contour of the medial and/or lateral trochlear ridges of the talus with or without radiolucent zones in the underlying subchondral bone
59
Degenerative Joint Disease
Talus
Radiographic findings:
* Periarticular osteophytosis
* Periosteal new bone formation
* Subchondral bone lysis and/or increased opacity of the spongiosa
* Decreased compactospongiosa demarcation
* Narrowing or loss of joint space
60
Standard Stifle radiographs
1. Lateromedial and/or flexed lateromedial
2. Caudocranial
3. Caudal 60º lateral-craniomedial oblique
4. Craniolateral-caudomedial oblique/caudomedial-craniolateral oblique
5. Cranioproximal-craniodistal (flexed) oblique
61
Foal Stifle
6 centers of ossification:
* Femur:
* Metaphysis
* Distal epiphysis
* Tibia:
* Proximal epiphysis
* Metaphysis
* Tibial tuberosity
* Patella
62
Craniocaudal
Stifle
63
Calcinosis Circumscripta
A condition characterized by one or more hard, circumscribed subcutaneous swellings, typically formed at the lateral aspect of the femorotibial joint. Lameness is not usually present with smaller lesions. If lameness is present, surgery may be indicated.
Radiographic findings:
* Lesion that is distinctly outlined mass of soft-tissue opaque
* Irregularly infiltrated weith small, highly opaque, amorphous granules
64
Slightly oblique lateral-lateral image and diagram of the pharyngeal region of a normal adult horse.
Rostral is to the left. Note that the caudal angles of the left and right mandibles are slightly separated, indicating slight obliquity. There is gas in the Eustachian tube diverticulum (etd) and the nasopharynx (np). The epiglottis (e), soft palate (sp) and stylohyoid bones (h) are clearly demarcated.
1. petrous temporal bone
2. external acoustic meatus
3. basioccipital bone
4. body of basisphenoid bone
5. pterygoid process
6. maxillary tuberosity
7. third upper molar tooth
8. third lower molar tooth
9. stylohyoid angle
10. stylohyoid
11. ceratohyoid
12. basihyoid
13. thyrohyoid
14. condyloid process of mandible
15. ramus of mandible, cranial edge
16. ramus of mandible, caudal edge
17. angle of mandible
18. mandibular foramen
19. mandibular canal
20. dorsal wall of pharynx
21. aryepiglottic fold
22. arytenoid cartilage
23. epiglottis
24. cranial wall of Eustachian tube diverticulum (guttural pouch)
25. caudal wall of Eustachian tube diverticulum (guttural pouch)
26. plica salpingopharyngea
27. laryngeal ventricles
28. soft palate
29. atlas (first cervical vertebra)
30. dens
31. axis (second cervical vertebra)
65
Right oblique image and diagram of the maxillary region of a normal 9-year-old Warmblood
Right oblique image and diagram of the maxillary region of a normal 9-year-old Warmblood. Rostral is to the left. The exposure was selected to highlight the detail of the tooth roots.
1. second right upper premolar
2. third right upper premolar
3. fourth right upper premolar
4. first right upper molar
5. second right upper molar
6. third right upper molar
7. second right lower premolar
8. third right lower premolar
9. fourth right lower premolar
10. first right lower molar
11. lamina dura
12. socket
13. rostral root
14. caudal root
15. buccal longitudinal crest and folds of peripheral enamel
16. interalveolar septum
17. occlusal surface
18. middle nasal meatus
19. infraorbital canal
20. nasomaxillary notch
21. hard palate
66
Lateral-lateral image and diagram of the rostral aspect of the head of a normal mature horse.
Dorsal is to the left.
1. second upper premolars
2. third upper premolars
3. second lower premolars
4. third lower premolars
5. upper incisor teeth
6. lower incisor teeth
7. body of mandible
8. area of mandibular symphysis
9. interalveolar margin of mandible
10. mandibular canal
11. nasal process
12. nasomaxillary notch
13. dorsal border of nasal process of incisive bone
14. interalveolar border of incisive bone
15. palatine process of incisive bone
16. ridge of hard palate
17. nostril
18. vestibulum oris
67
Lateral-lateral image and diagram of the cranium of a normal mature horse.
1. Dorsal is to the left. There is slight rotation of the mandible resulting in separation of the right and left condylar and coronoid processes.
2. coronoid process
3. condyloid process
4. stylohyoid
5. occipital condyle
6. ethmoid turbinates
7. hypoglossal foramen
8. temporomandibular articulation
9. petrous temporal bone
10. external acoustic meatus
11. basioccipital bone
12. body of basisphenoid
13. rami of mandibles
14. zygomatic process of temporal bone
15. zygomatic process of frontal bone
16. orbit
17. pterygoid process
18. cranium
19. frontal sinus
20. external occipital protuberance
21. external occipital crest
22. internal plate of frontal bone
23. caudal fossa of cranium
24. osseous temporal process
25. site of sphenopalatine sinus
68
Lateral-lateral image and diagram of the nasofrontal region of a normal adult horse, exposed to evaluate the paranasal sinuses rather than the tooth roots.
Dorsal is to the left.
1. nasomaxillary notch
2. nasal bone
3. frontal bone
4. orbit
5. facial crest
6. internal plate of frontal bone
7. dorsal nasal meatus
8. middle nasal meatus
9. ventral nasal meatus
10. infraorbital canal
11. conchal sinus septum
12. conchofrontal sinus
13. recess of dorsal nasal concha
14. sinus of ventral nasal concha
15. recess of ventral nasal concha
16. frontal sinus
17. margin of maxillary sinus
18. ethmoid turbinates
19. third upper molar tooth
20. cranial aspect of ramus of mandible
69
Ventrodorsal image and diagram of the cranium of a normal mature horse.
1. nuchal crest
2. jugular process
3. tympanic bulla
4. basilar part of occipital bone
5. rostral border of choanae
6. vomer
7. stylohoid
8. ethmoid turbinate region
9. zygomatic arch
10. caudal margin of orbit
11. mandible
12. condylar process of mandible
13. coronoid process of mandible
14. caudal border of ramus of mandible
15. axial margin of angle of mandible
16. third upper molar tooth
17. third lower molar tooth
70
Lateral-lateral image of the occipital region of a young Thoroughbred foal with a **firm swelling ventral to the ear**.
**Within the mass** a **tooth-like structure** can be seen (black arrow). This mass is a **dentigerous cyst ("teratoma")**. Note also the clearly demarcated spheno-occipital suture line between the basioccipital and basisphenoid bones (white arrow). This is usually closed by approximately 5 years of age.
_Dentigerous cyst:_
Dentigerous cyst (or temporal teratoma) are of highly variable shape and size and may be found in many positions. They frequently have an opaque core, composed of dental tissue, but may have less radiopaque tissue surrounding it. They are frequently found around the base of the eat and in close apposition temporal bones.
Dentigerous cysts are usually identified clinically as a mass or discharging sinus close to an ear. The introduction of a probe or contrast medium into the sinus is helpful in locating the site of the cyst. Dentigerous cyst can normally be removed surgically.
71
Temporohyoid Osteoarthropathy
Cause:
* The cause of temporohyoid osteoarthropathy is not known but **otitis media/interna, age-related** degeneration and **biochemical strain** on the temporohyoid joint have been proposed.
Clinical signs:
* Peripheral vestibular disease
* Facial nerve paralysis
Radiographic signs:
* Irregular increased opacity in the region of the acoustic meatus and articulation of the hyoid and petrous temporal bones +/- fracture of the stylohoid bone
* Bony proliferation in the region of the temporohyoid joint may be seen in an oblique projection
Pathophysiology:
* Once osseous proliferative changes have developed at the temporohyoid bone (hyoid apparatus) is restricted and physiologic movements may result in traumatic injury, including hemorrhage into the middle and inner ear. This may cause recurrence or exacerbation of clinical signs.
Treatment:
* Surgical resection of part of the stylohoid bone may give improvement of clinical signs
72
Nasofrontal suture separation/exostosis
General:
* Nasofrontal suture separation/extosis is relatively common in young horses but can also be seen in adults. There is frequently no history of trauma, but a hard swelling forms across the dorsal aspect of the head, level with or just rostral to the rostral aspect of the orbits.
On radiographs:
* Apperant on lateral-lateral image as a radiopaqye protuberance of calus forming in the region of the nasofrontal suture
* The calus can protrude both externally and internally, into assocaited sinuses or nasal passage
* Typically, the bone has greater opacity on either wiset of the sture
* Initially a radiolucent suture line may be evidence transversing new bone
* There may be concurrent involvememt of the nasolacrimal suture
* Ocassionally hemorrhage occurs, leaving fluid line within the maxillar sinus
* A degree of ephiphora may be present temporarily, or permanently, if the area of the suture affected involves the nasolacrimal duct
This lesion is of little clinical significance, but usually results in permanent disfigurement of the head.
73
Right oblique view of the frontal area of a 10-year-old Quarterhorse with a history of a slowly progressive deformity of the facial bones on the right side.
There is a well-circumscribed soft-tissue mass (arrows) rostral to the ethmoid turbinates (et), extending dorsally and deforming the nasal and maxillary bones. This soft-tissue mass is a **submucosal cyst.** The sinuses appear otherwise normal.
74
Ventrodorsal image of the head of a yearling Thoroughbred with stertorous breathing and an intermittent right-sided nasal discharge.
There is a large, well-circumscribed radiopacity in the right maxillary sinus (solid arrows), axial to the molar teeth. Note the deviation of the nasal septum to the left. There is also an ill-defined opacity (open arrows) abaxial to the molar teeth (compare with the left side).
_Diagnosis_: **maxillary sinus cyst.**
75
Orthogonal radiographs of the nasofrontal region of a yearling.
There is a soft-tissue opacity (arrows) dorsal to the most caudal upper cheek tooth, adjacent to, and summating with, the *ethmoid turbinates*. There is slight deviation of the nasal septum towards the right. The mass is an **ethmoid haematoma**.
Note that this projection is slightly oblique: the cheek teeth are at different levels.
76
Right lateral oblique image of the maxillary region of a 10-year-old Standardbred.
The horse had previously had the bulk of the fourth upper right cheek tooth removed, but a piece remains.
There is periapical lysis (rarefaction) around the caudal root of the third upper cheek tooth. Dorsal to the first upper right cheek tooth is an area of **dystrophic mineralisation** within the **conchal sinus**.
The rostral maxillary sinus and the ventral conchal sinus communicate via the conchomaxillary opening. Such dystrophic mineralisation (‘coral’) is invariably the result of chronic infection (usually dental in origin).
77
Lateral-lateral image of the nasofrontal region of an aged Thoroughbred with facial swelling.
There is a large opaque mass occupying the region of the frontal and maxillary sinuses and distorting the frontal and nasal bones.
The mass was identified as an **osteosarcoma** at post-mortem examination.
78
Orthogonal radiographs of the head of a 4-year-old Thoroughbred.
There is a well-demarcated partially mineralised soft tissue mass in the maxilla partially superimposed over the upper first two cheek teeth. The mass is of heterogeneous opacity, often described as a ‘foamy’ appearance.
Biopsy revealed this to be an **odontogenic tumour.**
79
Slightly oblique left lateral image of the nasofrontal region of a 3-year-old Thoroughbred with a recent history of **swelling below the left eye, left-sided mucoid nasal discharge** and **dyspnoea.**
There is a large mass of irregular opacity in the region of the most caudal upper cheek tooth. Within the mass are several opacities resembling teeth (arrows); et = ethmoid turbinates. Post-mortem examination confirmed that the mass was an **ameloblastic odontoma**.
80
Orthogonal projections of the rostral aspect of the head region of an aged pony with a **slowly enlarging facial swelling**.
There is a **cyst-like** lesion in the incisive bone (premaxilla), distorting its dorsal contour. The overlying cortex is thinned and has a slightly scalloped appearance caudally.
81
Intraoral image of the mandibular incisors.
There is marked irregular loss of opacity (dental substance) of the left canine tooth (204, arrow), typical of **equine odontoclastic tooth resorption and hypercementosis (EOTRH)**.
A combination of hypercementosis, demonstrated as a bulbous shape of the right first (central, 101) incisor root (arrowhead), and irregular resorption is also present. The right canine tooth has smoothly margined cementum proliferation.
82
Intraoral radiograph of the maxillary incisors and canines.
Note the large bulbous mass-like lesions of cementum surrounding the incisor and canine roots characteristic of hypercementosis, part of the **equine odontoclastic tooth resorption and hypercementosis complex**.
83
Left-right oblique image of the upper cheek teeth of a 7-year-old Thoroughbred with a firm **swelling of approximately 3 months**’ duration.
The caudal tooth roots of the second upper cheek tooth (107) (arrow) are poorly defined and the lamina dura is less well-defined caudally. The tooth was extracted and the caudal tooth root was filled with purulent material.
84
Open-mouth oblique image of the right upper cheek teeth of a 6-year-old Appaloosa which presented with **facial swelling and marked gingivitis**.
There is a space, a **diastema**, between the rostral two cheek teeth, 106 and 107.
85
Open-mouth oblique image of the right cheek teeth of an aged Welsh pony. **Two maxillary cheek teeth had previously been removed** from the left side, but **nasal discharge persisted.**
There is a very **irregular alignment of the occlusal surface** of the maxillary cheek teeth. This is wavemouth. Note the relatively short lengths of the reserve crowns typical of ageing horses.
86
Slightly oblique right-left lateral image of the mandible of a weanling Morgan with a history of a small mass developing on the mandible 6 weeks previously and enlarging progressively despite antimicrobial therapy.
There is a large expansile lesion of the mandible that has a reticulate or ‘foamy’ appearance. Post-mortem examination confirmed that this was the result of **osteomyelitis**, although its radiographic appearance was similar to that of an **odontoma, a reparative granuloma or an aneurysmal bone cyst.**
87
Lateral-lateral view of the head of a 3-year-old Thoroughbred colt with a **rapidly expanding mass** on the **cranial aspect of the ramus** of the left and right mandibles.
There is **extensive new bone** on the ventral aspect of the mandible and loss of the cortex. The rami of the mandible have a heterogeneous radiopacity. The lesions progressively resolved with time and non-steroidal anti-inflammatory treatment.
_Diagnosis_: **craniomandibular osteopathy.**
88
Slightly oblique right-left lateral radiograph of the skull of a 7-year-old Quarterhorse with a 3-month history of **swelling in the region of the left mandible** and **difficulty in chewing**.
There is a large lucent area (arrows) in the cranial angle of the left mandible. The bone adjacent to the margins of the defect appears lytic and irregular. The left stylohyoid bone (h) cannot be evaluated totally, but appears to be involved in the process. The approximate location of the normal cranial angle of the mandible is marked with a dotted line. The epiglottis (e) is normal.
Post-mortem examination confirmed the presence of a **squamous cell carcinoma**.
89
Lateral-lateral image of a head.
There is **luxation of the temporomandibular joints**.
The condylar processes of the mandibles (arrows) are displaced rostral to the mandibular fossae (arrowheads).
90
Intra-oral ventrodorsal image of the rostral mandible of a show pony.
There is a **displaced fracture** of the mandible involving the tooth roots of the right corner (103) and intermediate (middle, 102) incisors. Note that the root of the corner incisor is fractured.
91
Lateral-lateral image of the rostral aspect of the head of a 16-year-old riding horse which had been **kicked the previous day**.
The horse was dysphagic and there was a discharging wound. There is a c**omminuted fracture** of the horizontal ramus of the mandible (arrows), with overlying soft tissue swelling. An intra-oral radiograph more accurately defined the degree of comminution of the fracture.
92
lightly oblique lateral-lateral image of the mandibular region of a 14-year-old Arab which had **fallen in the stable** and showed **bleeding from the mouth and nose**.
There is a **comminuted fracture** of the vertical ramus of the mandible (arrows).
93
Slightly oblique lateral-lateral image of the horizontal ramus of the mandible of a 9-year-old Oldenburg who **would not ‘take the bit’ on the right rein**.
The dorsal cortex in the interdental space is poorly defined with loss of opacity (arrows), typical of a sequestrum.
94
Well-collimated lateral-lateral image of a **normal pharynx** of an immature horse.
The nasopharynx (np) contains air.
* epiglottis (e)
* thyrohyoid (1)
* basihyoid (2)
* ceratohyoid (3)
* stylohyoid (4)
NOTE: The soft palate normally sits ventral to the epiglottis because horses are obligate norse breathers.
95
Slightly oblique lateral-lateral image and diagram of the pharyngeal region of a **normal** adult horse
Note that the caudal angles of the left and right mandibles are slightly separated, indicating slight obliquity. There is **gas** in the **Eustachian tube diverticulum (etd)** and the **nasopharynx (np)**.
The epiglottis (e), soft palate (sp) and stylohyoid bones (h) are clearly demarcated.
1. petrous temporal bone
2. external acoustic meatus
3. basioccipital bone
4. body of basisphenoid bone
5. pterygoid process
6. maxillary tuberosity
7. third upper molar tooth
8. third lower molar tooth
9. stylohyoid angle
10. stylohyoid
11. ceratohyoid
12. basihyoid
13. thyrohyoid
14. condyloid process of mandible
15. ramus of mandible, cranial edge
16. ramus of mandible, caudal edge
17. angle of mandible
18. mandibular foramen
19. mandibular canal
20. dorsal wall of pharynx
21. aryepiglottic fold
22. arytenoid cartilage
23. epiglottis
24. cranial wall of Eustachian tube diverticulum (guttural pouch)
25. caudal wall of Eustachian tube diverticulum (guttural pouch)
26. plica salpingopharyngea
27. laryngeal ventricles
28. soft palate
29. atlas (first cervical vertebra)
30. dens
31. axis (second cervical vertebra)
96
Lateral-lateral image of the pharyngeal region of a **2-year-old** Thoroughbred with a history of **nasal discharge** and an **occasional cough**.
There is a fluid line (straight arrows) in one or both Eustachian tube diverticula. The ventral half of the diverticulum is uniformly opaque due to the accumulation of pus, i.e. **empyema**.
n the original radiograph there was a clearly irregular outline of the dorsal pharyngeal wall and the fine mottled opacities (curved arrow) in the dorsal nasal pharynx which represented pharyngeal lymphoid hyperplasia, but this cannot be seen in this reproduction. The epiglottis (e) is normal.
**Eustachian tube diverticulum empyema:**
* Although probably becoming a less common condition, Eustachian tube diverticulum empyema may be seen in areas with a larger population of horses. It usually follows a streptococcus infection, Particularly ***Streptococcus equi**.*
* Clinically there is usually a unilateral purulent nasal discharge. Empyema may fill one both pouches, giving an increase radiopacity of the diverticulum.
* There is normally a fluid line in the diverticulum, which also aid differentiation from a soft tissue mass.
* It is possibly to determine if the condition involves one or both pouches by obtaining ventrodorsal views. It may be easier, however, to obtain a lateral-lateral radiograph from the left and right sides. The radiographs compared for magnification and sharpness of the fluid line. The air cap appears larger and less sharp when away from the cassette.
* This condition should initially be treated conservatively but surgical drainage may be required.
97
Lateral-lateral image of the pharyngeal region of an 8-year-old pony
There are many well circumscribed opaque masses within the Eustachian tube diverticulum. These are **chondroids**, a sequel to Streptococcus equi infection.
98
Right lateral-lateral image of the pharyngeal region of a 1-month-old Arab. The soft tissues in the **parotid region** were noted to be **enlarged soon after birth** and **progressively enlarged** and became more fluctuant.
**Bilateral Eustachian tube diverticula tympany**.
_Eustachian tube diverticula tympany_:
* Most commonly seen in young animals.
* It generally presents clinically as a soft fluctuant swelling in the parotid area.
* In severe cases it may cause respiratory distress.
* This consitiona may arise from the present of excessice soft tissue at the pharyngeal orifice, whic acts as a valve and allows air into the pouch during degluttition but does not allow for the exit of air.
* As a sequel to the condition, there may be respiratory distress due to narrowing of the pharynx, and in some cases **aspiration pnuemonia**. For this reason **thoracic radiographs** should be obtained.
_Radiographic signs_:
* Radiographically it presents as grossly enlarged Eustachian tube diverticulum, extending caudal to the atlas.
* There is some rounding of the outline of the diverticulum and often narrowing of the nasopharynx.
* Generally the conditiona is unilateral but occasionally it is bilateral
99
Lateral-lateral image of the pharyngeal region of a 4-year-old Quarterhorse with a 3-day history of **dysphagia**. Clinical examination revealed **eighth and ninth cranial nerve deficits** and **bilateral nasal discharge** containing food.
The ventral margins of the Eustachian tube diverticula (ETD) are irregular (straight arrows) and there is soft-tissue swelling in the retropharyngeal area impinging on the ventral caudal aspect of the ETD (curved arrows).
There is air in the oesophagus (o) and the lateral saccules (l). The stylohyoid bones (h) are normal.
The caudal ventral soft-tissue mass is due to **retropharyngeal lymphadenopathy** and **local inflammation**, caused by infection with **Streptococcus equi.**
100
Lateral-lateral radiograph of the pharyngeal region of a 15-year-old Quarterhorse. The mare had exhibited t**ransient facial nerve paralysis 12 months** **previously**, which had **recently recurred**.
There is bony proliferation on the stylohyoid (white arrow). Such bony proliferation may be visible endoscopically via the guttural pouch.
There is also a **pathological, delayed union fracture** with callus further distally (black arrow), which is unable to heal due to constant movement of the stylohyoid bone.
Note the **flaring of the ends of the bon**e at the fracture site (black arrow) and slight increased opacity along the fracture margins, typical of a delayed union.
A normal epiglottis is partially superimposed over the distal fracture piece.
101
Lateral-lateral image of the pharynx of an 11-year-old Thoroughbred with a history of **persistent salivation** and **food reflux**.
There is **entrapment of the epiglottis** by the aryepiglottic folds (arrows). Endoscopic examination revealed marked thickening and ulceration of the aryepiglottic folds, and confirmed entrapment of the epiglottis. There was also moderate, diffuse pharyngitis. There is some ill-defined mineralization within the arytenoid cartilages (incidental).
_Epiglottic entrapment:_
* With epiglottic entrapment the apex and lateral margins of the epiglottis become enveloped by the ventral mucosa and aryepiglottic folds.
* The radiographic appearance is varied, but the **epiglottis always appears blunted** and **shortened**.
* It should be confirmed by endoscopy and must be differentiated by shortening of the epiglottis.
* There may be concurrent dorsal displacement of the soft palate, but this is inconsistent.
* Clinically the horse shows exercise intolerance **and** abnormal respiratory sounds at high speeds, but asymptomatic at rest.
* Treatment is surgical and there is reasonable prognosis.
102
Lateral-lateral image of the pharyngeal region of a **1-month-old** Standardbred colt, with a history of **dyspnoea following suckling** or **strenuous exercise**.
There is a smoothly outlined soft-tissue opacity (arrows), ventral to the epiglottis (e), in the oropharynx. The mass, a **subepiglottic cyst**, appears to displace the soft palate (sp) dorsally above the epiglottis, but the area between the soft palate, epiglottis and subepiglottic cyst cannot be defined. Note air in the esophagus (o) and the trachea (t).
_Subepiglottic cysts:_
* Are believed to arise from remnants of the thyroglossal duct.
* They are **well-circumscribed radiopaque (soft-tissue) masses under the ventral aspect of the base of the epiglottis which displace the epiglottis in a caudodrosal direction.**
* Treatment is surgical and the prognosis is reasonable.
103
Lateral-lateral image of the pharyngeal region of an **11-year-old** hunter with a history of **exercise intolerance** and an **abnormal respiratory noise**.
Endoscopic examination of the larynx revealed **distortion in shape of the arytenoid cartilages**, i.e. **arytenoid chondropathy (chondritis).**
Radiographically there is extensive well-defined soft-tissue swelling (arrows) on the craniodorsal aspect of the larynx. There is some ill-defined mineralization within the arytenoid cartilages (arrowheads) - incidental.
_Arytenoid chondritis:_
* Arytenoid chondritis causes exercise intolerance and abnormal respiratory noise.
* The arytenoid cartilages may have a mottled increase in opacity or irregular outline, particularly of the cranial margin of the cartilage. They may also have some mineralization, which may occasionally be seen incidentally in old animals, where there is more generalized involvement throughout the laryngeal cartilages.
* Ultrasonography of the larynx reveals enlargement and changes in echogenicity (hyperechogenic) or the arytenoid cartilages.
* If the condition is unilateral in a breeding horse it may be treated conservatively, but surgery is usually required to return a horse to athletic function or if the condition is bilateral.
104
Lateral-lateral image of the pharyngeal region of an aged Thoroughbred.
The soft palate (s) is displaced dorsal to the epiglottis (e).
**Dorsal displacement of the soft palate**:
* May be intermittent or persistent, with the soft palate located dorsal to the epiglottis.
* The presence of air between the tongue and soft palate is usually the first radiograph abnormality noted. Careful examination of the radiograph may show the caudal part of the soft palate lying over the epiglottis.
* This is a dynamic condition and so may be seen on plain radiographs. It is most likely to be demonstrated immediately after the horse swallows and may be more easily confirmed by endoscopy.
105
* Lateral-lateral radiographic image of the mid-neck region (cervical vertebrae C4–C6) of a normal mature horse.
* The vertebral foramen is approximately rectangular in shape.
* The small bony protuberance on the craniodorsal aspect of the vertebral bodies is a normal variant.
* IVF = intervertebral foramen
* MSD = minimum sagittal diameter
* C4 = fourth cervical vertebra
* C5 = fifth cervical vertebra
* C6 = sixth cervical vertebra
106
Method to obtain the sagittal ratio of the vertebral foramen:
* Divide the minimum sagittal diameter (MSD) (a) by the dorsoventral height (b) of the corresponding vertebral body at biggest point of its cranial aspect.
Method to obtain the sagittal ratio of the vertebral foramen:
* Divide the minimum sagittal diameter (MSD) (a) by the dorsoventral height (b) of the corresponding vertebral body at biggest point of its cranial aspect.
107
Measurement of the intervertebral diameter, the distance between the cranioproximal aspect of the physis of the cranial aspect of the vertebral body and the ventrocaudal aspect of the lamina of the immediately cranial vertebra (a).
The height of the widest part of the cranial aspect of the vertebral head (b) is also measured.
The **intervertebral sagittal ratio** is calculated by dividing the minimum intervertebral distance by the maximum height.
Measurement of the intervertebral diameter, the distance between the cranioproximal aspect of the physis of the cranial aspect of the vertebral body and the ventrocaudal aspect of the lamina of the immediately cranial vertebra (a).
The height of the widest part of the cranial aspect of the vertebral head (b) is also measured.
The **intervertebral sagittal ratio** is calculated by dividing the minimum intervertebral distance by the maximum height.
108
Method to obtain a **corrected minimum sagittal diameter** (cMSD).
* The absolute (measured) MSD (a) is divided by the length (b) of the corresponding vertebral body.
Method to obtain a **corrected minimum sagittal diameter** (cMSD).
* The absolute (measured) MSD (a) is divided by the length (b) of the corresponding vertebral body.
109
Separate center of ossification for the
dens of the axis
* Lateral-lateral image of the cranial cervical vertebrae (C1–C3) of a 5-day-old foal.
* Note the separate centre of ossification (arrow) of the dens of the axis (C2).
* The cranial and caudal physes of C2 and C3 are open.
110
Lateral-lateral image of the cranial cervical vertebrae of a normal adult horse.
There is a large spur (arrow) which appears to be on the dorsocaudal aspect of the vertebral body of the axis (C2), protruding into the vertebral canal. It is actually part of the transverse process and is an **incidental radiological finding**.
111
Lateral 50° dorsal-lateroventral oblique image of the fifth to seventh cervical vertebrae acquired from left to right of a normal adult horse:
* The right articular process joints are projected at the top of the image.
* Note that there is a separate centre of ossification on the ventrocaudal aspect of the vertebral body of the sixth cervical vertebra, a normal variant.
Lateral 50° ventral-laterodorsal oblique image and diagram of the fourth to sixth cervical vertebrae acquired from left to right of a normal adult horse:
* The left articular process joints are projected at the top of the image and are smoothly marginated.
* The intervertebral foramina are large and well-demarcated.
* Note that the right **articular process joints** are not of uniform width, tending to be **wider cranially**.
* However, each articular process is of similar craniocaudal length and the subchondral bone plates are of uniform opacity.
112
Lateral 50° dorsal-lateroventral oblique image of the fifth to seventh cervical vertebrae acquired from right to left of a 13-year-old Thoroughbred with **mild hindlimb ataxia, left-sided weakness** and **mild forelimb lameness**.
The left articular process joints are projected at the top of the image.
The left articular process joint between the sixth and seventh cervical vertebrae is enlarged with irregular periarticular new bone formation (arrows); the intervertebral foramen is narrowed.
113
**Lateral 50° dorsal-lateroventral obliq**ue image of the sixth to seventh cervical vertebrae acquired **from right to left** of a 7-year-old Thoroughbred.
The **right articular process joint is abnormal** with an irregular joint surface of the caudal articular process of the sixth cervical vertebra, and modelling of its caudal margin (arrow).
114
Lateral-lateral image of the occiput and the cranial cervical vertebrae (C1–C2) of a 6-year-old Warmblood gelding showjumper with **neck stiffness**. The horse **had to** **straddle its forelimbs in order to graze**.
The atlas (C1) is **fused** to the occiput and the axis (C2) is partially duplicated and misshapen – an occipito-atlanto-axial malformation.
(See normal below for comparison)
115
Lateral-lateral image of the second to fifth cervical vertebrae of a 6-year-old Warmblood stallion with **mild hindlimb ataxia**, obtained with the horse standing normally.
* There is **subluxation** of the third and fourth cervical vertebrae (white arrow) with narrowing of the minimal sagittal diameter of the vertebral canal.
* Note also the **severe caudal extension of the vertebral arc**h of the third cervical vertebra (black arrow), which **extends beyond the cranial physis** of the vertebral body of the fourth cervical vertebra, and the ‘ski jump’ appearance of the dorsocaudal aspect of the vertebral body of the third cervical vertebra.
116
Lateral-lateral image of the caudal cervical vertebrae (C5–C7) and first thoracic vertebra of a 6-year-old Thoroughbred novice event horse presented because of **difficult behaviour** and **poor performance**. Clinical examination revealed **mild hindlimb ataxia** and **weakness**.
* There is **dorsal subluxation** of the seventh cervical vertebra and reciprocal extension between the seventh cervical and first thoracic vertebrae.
* The **articular process joints** between the sixth and seventh cervical vertebrae are **enlarged** and have **focal radiolucent areas**.
* The **intervertebral foramina are narrowed** caudally.
* The vertebral foramen of the seventh cervical vertebra is wedge-shaped, narrower cranially.
117
Right lateral-left lateral image of the sixth cervical to first thoracic vertebrae of a 7-year-old Warmblood dressage horse with **hindlimb ataxia, neck stiffness** and **dermatomal sweating** on the right side of the neck.
* There is **massive asymmetrical enlargement** of the **articular process** joints of the sixth and seventh cervical vertebrae and the seventh cervical and first thoracic vertebrae.
* There is **ventral buttressing and narrowing** of the **intervertebral foramina**, especially at C6–C7.
* There is a well-rounded fragment, a **chronic fracture**, on the dorsal aspect of the articular process joints of the sixth and seventh cervical vertebrae.
118
Lateral-lateral image of the caudal cervical vertebrae (C6 and C7) of an ataxic yearling Thoroughbred filly.
* There is extensive modelling of the articular process joints of C6–C7 and an irregular joint contour.
* Radiolucent areas (solid arrows) represent pits in the vertebral pedicles.
* Spinal cord compression was confirmed at C6–C7, associated with a synovial cyst.
* One ventral process, with a separate centre of ossification, was transposed from C6 to C7 (open arrow).
119
Lateral-lateral image of the caudal cervical vertebrae (C5–C7) of a 7-year-old Warmblood with **generalised stiffness**.
There is **considerable enlargement** of the **articular process joints** between the fifth and sixth and sixth and seventh cervical vertebrae, with **almost complete obliteration** of the **intervertebral foramina**.
120
Lateral-lateral image of the fifth and sixth cervical vertebrae of an **ataxic** 9-year-old Thoroughbred cross riding horse
* There is a **chronic fracture** involving the articular process of C5–C6 (arrows).
* The articular process joints are enlarged with ventral buttressing and obliteration of the intervertebral foramen.
* Note the well-defined radiolucent area in the pedicle of the fifth cervical vertebra.
121
Lateral-lateral image of the cranial cervical vertebrae (C1–C2) of a 9-year-old advanced event horse with **severe neck stiffness** and **an audible click** associated with these vertebrae.
* There is **subluxation** of the **atlantoaxial joint**.
* Note the **narrowed space** between the dorsal aspect of the odontoid peg of the axis and the ventral aspect of the dorsal lamina of the atlas (arrowed).
* There is slight irregularity of the dorsal contour of the odontoid peg.
* Post mortem examination confirmed complete **rupture of the ligament of the dens**.
122
Lateral-lateral image of the caudal cervical vertebrae (C6–C7) of a 15-year-old Thoroughbred stallion with a history of **difficulty in mounting mares** and a non-specific **hindlimb gait abnormality**.
Clinical examination revealed mild hindlimb ataxia and weakness.
* The **intercentral joint** space is **narrowed ventrally**.
* There is **periarticular new bone** on the caudoventral aspect of the body of the sixth cervical vertebra and modelling of the dorsal articular margin consistent with degenerative joint disease.
* There is **enlargement of the articular process joints** between the sixth and seventh cervical vertebrae with ventral buttressing.
123
Lateral-lateral image of the third to sixth cervical vertebrae of a 5-year-old Thoroughbred mare with **severe neck stiffness, persistent leucocytosi**s and neutrophilia, and an **increase in ß2 globulins**.
There are irregular radiolucent areas in the vertebral bodies (arrows) surrounded by bone of increased opacity.
**Tuberculous osteomyelitis** was confirmed post-mortem.
124
Lateral-lateral image of the sixth cervical to second thoracic vertebrae of a 4-year-old pony with **severe neck stiffness** and great **difficulty in lowering its head** to graze.
* There is **complete loss of the intercentral joint space** between the seventh cervical (C7) and first thoracic (T1) vertebrae.
* The **caudal end plate** of C7 and the head of the vertebral body of T1 are **misshapen**.
* There is a **lucent area** in the head of T1 with generalised surrounding increased opacity. T
* he dorsal profile of the vertebral body of C7 is of abnormal shape.
* There is transposition of a ventral process onto the vertebral body of C7.
* There is also **considerable enlargement of the articular process joints** between the seventh cervical and first thoracic vertebrae.
* The pony’s ability to lower the neck was improved after intra-articular analgesia of the articular process joints between C7 and T1.
Discospondylitis
125
Lateral-lateral image of the first to third cervical vertebrae of a 24-year-old pony with **sudden-onset ataxia** and **neck stiffnes**s.
* There is **multifocal osteolysis** in the vertebral body of the second cervical vertebra, suggestive of **neoplasia**.
* Post-mortem examination confirmed the presence of a **large extradural soft tissue mass** at the level of C2 within the right side of the vertebral canal, displacing and compressing the spinal cord towards the left and slightly dorsally.
* The mass was confirmed as **lymphosarcoma**.
126
Slightly oblique lateral-lateral image of the mid-cervical region of a mature horse
There is diffuse **mineralization in the soft tissues secondary to an intramuscular injection** (arrow).
This radiopacity is partially superimposed on the articulation between C4 and C5 and should not be confused with a lesion involving the vertebrae.
_Soft tissue mineralization_:
* This may occur secondary to intramuscular injection or as a result of previous trauma
* A common site is in the nuchal ligament, caudal to the occiput
* Tearing of muscle and ligamentous insertions on the ventral aspect of the vertebral bodies may result in enthesophyte formation, readily identifiable radiographically on lateral-lateral projection
127
Lateral-lateral image of the fourth to sixth cervical vertebrae of a 10-year-old Arab endurance horse.
There is a **chronic complete displaced fracture** of the caudoventral aspect of the vertebral body of the fourth cervical vertebra, of no current clinical significance.
128
Lateral-lateral image of the third to fifth cervical vertebrae of a 9-year-old Dutch Warmblood dressage horse with **severe neck pain and stiffness**, and **incoordination following a fall** in a field 12 days previously.
There is a **comminuted, slightly displaced fracture** of the dorsal arch of the fourth cervical vertebra.
129
Lateral-lateral image of the summits of the spinous processes of the mid-thoracic region (T8–T13). Cranial is to the left. This 7-year-old Warmblood had **chronic back pain**.
There is separation of a **thin radiopaque flake** on the **dorsal** aspect of two **spinous processes** (T10 and T11, arrows), which is believed to **reflect elevation of the periosteum** following **damage to the supraspinous ligament**.
Note also the mild irregular entheseous new bone on the bodies of the spinous processes of T9 and T10, normal variants.
130
Lateral-lateral image of the spinous processes of the cranial thoracic vertebrae (T5-11) of a **normal adult horse**.
Note the **entheseous new bone** on the cranial and caudal margins of the spinous processes at the insertions of the **interspinous ligaments**, an incidental finding.
Compare with Figures 12.39, 12w.50(a)(ii) and 12w.50(a)(iii) (normal) and with Figures 12.50(b) and 12.50(c) in which the entheseous new bone involves **more caudal spinous processes, which is abnormal and of more likely clinical significance.**
131
Lateral-lateral image of the spinous processes of the second to sixth thoracic vertebrae of an advanced event horse with acute onset of pain in the withers region following a **fall in water**, and subsequently becoming cast in a stable within 24 hours.
There are **displaced comminuted fractures** of the **spinous processes** of T2–T6 (also 7–9, not shown). The horse was treated conservatively and made a complete functional recovery, although slight malformation of the withers region persisted.
